In recent years, liquid crystal display devices are widely used as display units for computers and home appliances such as televisions. Generally, a liquid crystal display device includes a liquid crystal display panel and an illumination device (backlight device) that is disposed on the rear side the liquid crystal display panel to illuminate light thereto. As this type of illumination device, a side-light type (edge-light type) illumination device is known. The side-light type illumination device includes a light guide plate and light sources provided along one side or a plurality of sides of the light guide plate. Such a side-light type illumination device has greater advantages such as being made thinner with ease, as compared with a direct-light type illumination device in which the light source is disposed on the rear side of the liquid crystal display panel.
In particular, a side-light type illumination device that uses an LED (light-emitting diode) as a light source is drawing attention for having advantages such as a longer life and a higher light-emitting efficiency.
Conventionally, in the side-light type illumination device, a so-called scanning type light-emitting method has been proposed to mitigate a deterioration in image quality such as moving images being blurry when displaying moving images in the liquid crystal display device. In the scanning type light-emitting method, the illumination device is divided into a plurality of regions, and the plurality of divided regions are sequentially caused to emit light. FIG. 7 is a front view showing a schematic configuration of an illumination device used for such a scanning type light-emitting method, and FIG. 8 shows cross-sectional views illustrating assembly steps for components of the illumination device.
As shown in the figures, an illumination device 50 includes a chassis 51 that is formed in a shallow box shape, and in the chassis 51, a plurality of light guide plates 52 having a rectangular shape longer in the horizontal direction are stored while arranged along the short side direction. At the side end faces of the respective light guide plates 52, a plurality of LEDs 53 that emit white light are disposed. Each light guide plate 52 has light-receiving faces 52a through which light from the LEDs 53 enters, and a light-emitting surface 52b that emits light entered through the light-receiving faces 52a upward (in an illumination direction). The light-receiving faces 52a are constituted of side end faces on the shorter sides of the light guide plate 52, and the light-emitting surface 52b is constituted of a front surface of the light guide plate 52. A reflective sheet 55 is disposed to cover rear surfaces 52c of the light guide plates 52 that are on the opposite side to the light-emitting surfaces 52b (see FIGS. 8(b) and 8(c)).
In the illumination device 50 of a divided light guide plate type in which the light guide plate, which is generally constituted of a single plate, is divided into a plurality of parts, in order to improve a problem of blurry moving images in displaying moving images, the LEDs 53 are sequentially lit in the top to bottom direction in synchronization with a scanning signal of a not shown liquid crystal display panel, thereby causing the respective light guide plates 52 to sequentially emit light in the top to bottom direction.
Such light guide plates 52 are fixed to a bottom plate 51a of the chassis 51 by support members 54. As shown in FIG. 8(a), each support member 54 has a plate-shaped base 54a, hooks 54b disposed on the lower surface of the base 54a, and holding parts 54c that rise from the upper surface of the base 54a. At the tip of each holding part 54c, a locking piece 54d that is elastically deformable is disposed so as to extend at a downward angle. In this configuration, steps 52d, 52d are formed along the respective longer side edges of the light guide plate 52. The steps 52d are formed to be recessed from the upper surface (light-emitting surface 52b) of the light guide plate 52.
As shown in FIG. 8(c), the lower ends of the locking pieces 54d of the holding parts 54c make contact with the upper surfaces of the steps 52d of the light guide plates 52 having the above-mentioned configuration. In the bottom plate 51a of the chassis 51, attachment holes 51b are formed, and the hooks 54b of the support members 54 are inserted and engaged in the attachment holes 51b. 
Steps to store and fix the plurality of light guide plates 52 into the chassis 51 in the above-mentioned illumination device 50 will be explained with reference to FIG. 8. As shown in FIG. 8(a), first, the hooks 54b of the support member 54 are engaged in the attachment holes 51b in the bottom plate 51a of the chassis 51, thereby fixing the support member 54 to the bottom plate 51a of the chassis 51 in a prescribed position.
Next, as shown in FIG. 8(b), the reflective sheet 55 is placed on the base 54a of the support member 54. The reflective sheet 55 has openings formed therein as inserting holes 55a through which the holding parts 54c of the support member 54 can be inserted. By inserting the holding parts 54c of the support member 54 through these inserting holes 55a, the reflective sheet 55 is fixed in a prescribed position on the bottom plate 51a of the chassis 51. Thereafter, by lowering the light guide plates 52 in proper positions between adjacent holding parts 54c, 54c of the support member 54, as shown in FIG. 8(c), the holding parts 54c, 54c of the support members 54 engage the steps 52d, 52d of the light guide plates 52, and as a result, the light guide plates 52 are fixed in prescribed positions. Related art documents for the present invention include Patent Document listed below.